hang on drop index

Summary

never end the drop command

Content

I have on the database this index 

SQL> select index_name from user_indexes;

INDEX_NAME
--------------------------------------------------------------------------------
SYS_IL0000031667C00005$$
SYS_IL0000031667C00004$$
DATI_ROMA_SEGNALAZIONI_SIDX

I'm trying to drop this index 

SQL> drop index DATI_ROMA_SEGNALAZIONI_SIDX;

but the command never end , could you explain hot to resolve .

The DDL  of index is :

CREATE INDEX DATI_ROMA_SEGNALAZIONI_sidx ON DATI_ROMA_SEGNALAZIONI(json_value(DETTAGLI_JSON, '$.geometry' RETURNING SDO_GEOMETRY ERROR ON ERROR))
  INDEXTYPE IS mdsys.spatial_index;

Version

19c